package io.renren.util;


import java.util.Random;


/**
 * @author huangj 2009-12-16
 */
public class RandomUtils {

    public static final String allChar    = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

    
    public static final String allLowerChar    = "0123456789abcdefghijklmnopqrstuvwxyz";
    
    public static final String letterChar = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

    public static final String numberChar = "0123456789";


    /**
     * 生成一个10位数的随机数
     * 
     * @return
     */
    public static String generateTmpEntityId() {

        return generateString(10);
    }


    /**
     * 返回一个定长的随机字符串(只包含大小写字母、数字)
     * 
     * @param length
     *            随机字符串长度
     * @return 随机字符串
     */
    public static String generateString(int length) {

        StringBuffer sb = new StringBuffer();
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            sb.append(allChar.charAt(random.nextInt(allChar.length())));
        }
        return sb.toString();
    }
    
    
    public static String generateNewLowerString(int length) {

        StringBuffer sb = new StringBuffer();
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            sb.append(allLowerChar.charAt(random.nextInt(allLowerChar.length())));
        }
        return sb.toString();
    }


    public static String generateNumString(int length) {

        StringBuffer sb = new StringBuffer();
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            sb.append(numberChar.charAt(random.nextInt(numberChar.length())));
        }
        return sb.toString();
    }


    /**
     * 返回一个定长的随机纯字母字符串(只包含大小写字母)
     * 
     * @param length
     *            随机字符串长度
     * @return 随机字符串
     */
    public static String generateMixString(int length) {

        StringBuffer sb = new StringBuffer();
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            sb.append(allChar.charAt(random.nextInt(letterChar.length())));
        }
        return sb.toString();
    }


    /**
     * 返回一个定长的随机纯小写字母字符串
     * 
     * @param length
     *            随机字符串长度
     * @return 随机字符串
     */
    public static String generateLowerString(int length) {

        return generateMixString(length).toLowerCase();
    }


    /**
     * 返回一个定长的随机纯大写字母字符串
     * 
     * @param length
     *            随机字符串长度
     * @return 随机字符串
     */
    public static String generateUpperString(int length) {

        return generateMixString(length).toUpperCase();
    }


    /**
     * 生成一个定长的纯0字符串
     * 
     * @param length
     *            字符串长度
     * @return 纯0字符串
     */
    public static String generateZeroString(int length) {

        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < length; i++) {
            sb.append('0');
        }
        return sb.toString();
    }


    /**
     * 根据数字生成一个定长的字符串，长度不够前面补0
     * 
     * @param num
     *            数字
     * @param fixdlenth
     *            字符串长度
     * @return 定长的字符串
     */
    public static String toFixdLengthString(long num, int fixdlenth) {

        StringBuffer sb = new StringBuffer();
        String strNum = String.valueOf(num);
        if (fixdlenth - strNum.length() >= 0) {
            sb.append(generateZeroString(fixdlenth - strNum.length()));
        } else throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth + "的字符串发生异常！");
        sb.append(strNum);
        return sb.toString();
    }


    /**
     * 根据数字生成一个定长的字符串，长度不够前面补0
     * 
     * @param num
     *            数字
     * @param fixdlenth
     *            字符串长度
     * @return 定长的字符串
     */
    public static String toFixdLengthString(int num, int fixdlenth) {

        StringBuffer sb = new StringBuffer();
        String strNum = String.valueOf(num);
        if (fixdlenth - strNum.length() >= 0) {
            sb.append(generateZeroString(fixdlenth - strNum.length()));
        } else throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth + "的字符串发生异常！");
        sb.append(strNum);
        return sb.toString();
    }

    // public static void main(String[] args) {
    // System.out.println(generateString(15));
    // System.out.println(generateMixString(15));
    // System.out.println(generateLowerString(15));
    // System.out.println(generateUpperString(15));
    // System.out.println(generateZeroString(15));
    // System.out.println(toFixdLengthString(123, 15));
    // System.out.println(toFixdLengthString(123L, 15));


    /** 根据指定几率随机取值 */
    public static boolean roll(double rate) {

        boolean flag = false;
        Random random = new Random();
        int total = 100000;
        double r = random.nextInt(total);
        if (r < total * rate) {
            flag = true;
        }

        return flag;
    }
}
